Abstract
We use lattice simulations to compute the baryon spectrum of SU(4) lattice gauge theory coupled to dynamical fermions in the fundamental and two-index antisymmetric (sextet) representations simultaneously. This model is closely related to a composite Higgs model in which the chimera baryon made up of fermions from both representations plays the role of a composite top-quark partner. The dependence of the baryon masses on each underlying fermion mass is found to be generally consistent with a quark-model description and large-Nc scaling. We combine our numerical results with experimental bounds on the scale of the new strong sector to derive a lower bound on the mass of the top partner.
Highlights
In this paper, we compute the baryon spectrum of SU(4) gauge theory with simultaneous dynamical fermions in two distinct representations, the fundamental 4 and the twoindex antisymmetric 6, which is real
We use lattice simulations to compute the baryon spectrum of SU(4) lattice gauge theory coupled to dynamical fermions in the fundamental and two-index antisymmetric representations simultaneously
Masses of single-representation baryons Mr are plotted as functions of the corresponding axial Ward identity (AWI) fermion mass mr
Summary
We compute the baryon spectrum of SU(4) gauge theory with simultaneous dynamical fermions in two distinct representations, the fundamental 4 and the twoindex antisymmetric 6, which is real. The dependence on the number of fermions could be much more dramatic near the edge of the conformal window, but based on a perturbative study of the two-loop β-function for the ’t Hooft coupling g2Nc, the present system compares most closely to SU(3) with between 4 and 5 fundamental fermions while the full Ferretti model is most similar to SU(3) with 6 fundamental fermions Based on these considerations, as well as our own previous detailed calculations of the meson spectrum [25], we believe that the theory we study is reasonably QCD-like, and expect that simulations with the precise fermion content of Ferretti’s model would be numerically close to our results. Technical aspects of the lattice simulation appear in Appendix B
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